Apparatus for repetitive application of a controlled force



'Nov. 7, 1967 c. E. BARKER 3,351,047

APPARATUS FOR REPETITIVE APPLICATION OF A CONTROLLED FORCE Filed March 9, 1965 INVENTOR CHARLES E BARKER zigJ w-n Sheets-Sheet 1 Nov. 7, 1967 I c. E. BARKER 3,351,047

APPARATUS FOR REPETITIVE APPLICATION OF A CONTROLLED FORGE Filed March 9/1965 5 Sheets-Sheet INVENTOR CHARLES E BARKER Ma ia? vc. E. BARKER 3,301,047

APPARATUS FOR RBPETITIVE APPLICATION OF A CONTROLLED FORCE Nov. 7, 1967 Filed March 9, 1965 V 6 5.; m; d

INVE NTOR CHARLES E. BARKER ZMJ f C m/1M Unitcd States Patent 3,351,047 APPARATUS FOR REPETITIVE APPLICATION OF A CONTROLLED FORCE Charles E. Barker, 202 29th Ave. SE., Calgary, Alberta, Canada Filed Mar. 9, 1965, Ser. No. 438,309 Claims. (Cl. 125-20) ABSTRACT OF THE DISCLOSURE Apparatus to apply a controlled force e.g. to urge a lapidary drill against a stone, and periodically to release that force to bob the drill. A counterweight, greater than the weight of the drill and associated moving elements, connected to apply a force tending to move them upwards with additional connection of the counterweight to tend to move the elements downwards, and automatic means to cause successive periodic predomination of upward and downward forces. Adapted also to spot gluing operations.

Background of the invention My invention relates to apparatus for repetitive application of a controlled force.

It is well adapted to embodiment in apparatus for drilling and circle cutting precious stones, but is capable of embodiment in other types of apparatus.

The art of drilling, circle cutting, and polishing precious stones extends to remote antiquity. The bow drill, possibly with hollow bits, is said to have been used as early as 3000 B.C.

In such operations as carried out at the present time some form of drill press is commonly used, often with manual means of applying a force to urge the bit against the Work, and to advance the bit as it penetrates. Excellent manual apparatus of various kinds is available for this purpose. Automatic and semi-automatic apparatus too is available which apparatus resembles generally a machinists drill press. In working with precious stones it is required to raise the bit at frequent intervals to permit fresh grit to flow to the cutting elements, and to re-engage the bit with the work. While this can be done by hand, automatic bobbing means would be an obvious advantage. A number of mechanisms have been developed to this end.

There has been, in recent years, substantial growth in the lapidary art as a hobby. While, as above implied, excellent work can be done with manual bobbing, and manually applied force, the whole operationand particularly -bobbing-is tedious and requires meticulous care from the operator. Hence there is need of a cheap automatic drilling machine which can not only drill holes in precious stones, but accomplish the operations of circle cutting, polishing, and so on, since the good commercial machines are too expensive for most amateur devotees of the art.

The use of a counterweight in apparatus of this kind, and in other apparatus, is well known. Generally the counterweight is operatively connected to a moving element, usually a vertically moving element carrying a rotating tool, in such a manner that there is but a small unbalanced force to be overcome in imparting lineal motion of translation thereto.

Summary of the invention I employ a counterweight so connected, which counterbalance is heavier than the moving element. Thus the 3,351,047 Patented Nov. 7, 1967 counterweight, acting alone, would move ment upwards.

As well as the operative connection of the counter weight as aforesaid, which I refer to as a pull up moving means, I provide an additional operative connection of the counterweight to the moving element, a pull down moving means, which acts in opposition to the pull up means, and tends to cause downward movement of the moving element. Thus, the system will come to rest at a particular position depending upon the relative effective lengths of the pull up and pull down moving means. This being so, periodic alteration of the elfective length of a said moving means will cause the moving element periodically to move from the equilibrium position, that is to bob. I have devised structure by means of which a cam, rotated by speed reduction means actuated by rotation of a shaft carrying the bit or tool, oscillates a pivoted lever to cause alteration of the effective length as aforesaid. Other means may be used to accomplish this end.

Accordingly, it is an object of my invention to provide structure as above indicated to accomplish bobbing.

A further object of my invention is to provide structure to alter the equilibrium position independently of the bobbing action. This I do by providing adjustable means of attachment of a moving means aforesaid to the counterweight, thus to alter the effective length of the moving means, so to advance or withdraw the bit or tool. In a moving means aforesaid including a cable, attachment of the cable to a rotatable drum of the counterweight, arranged so that rotation of the drum alters the effective length of the moving means, is convenient and satisfactory. The drum means may be attached to the moving element rather than the counterweight. and a number of obvious equivalents to this particular structure will be apparent to those skilled in the art.

The arrangements above provide for bobbing, and for advancement and withdrawal of the tool from the work independently thereof. A still further object of my invention is to provide means to urge the tool against the work with a controllable force, and to maintain substantially that force as the tool penetrates the work.

I attain regulation by providing a resilient regulating means as an operative element of a moving means aforesaid. As later will be explained in detail, when the tool is advanced to contact the work by rotation of the drum as above, upon further rotation of the drum, a force equal to the weight of the counterweight, plus the weight of the vertically moving element, would develop between the tool and the work. I insert a resilient regulating means in the pull down means, for instance a helical spring. Now, upon rotating the drum after initial contact, the force above is not developed, instead the extension of the spring changes. The force developed depends upon the strength of the spring, and the extent to which the drum is rotated further to extend the spring. Equivalent results will be attained by having the resilient regulating means as an operating part of the pull up means.

The aforesaid resilient regulating means also accomplishes automatic advancement of the tool as it penetrates the work, and maintains a sensibly constant force-since the force will change only by the small amount resulting from change in the spring extension due to penetration.

Apparatus constructed to embody the foregoing principles will thus repetitively apply a controlled force. In a drill embodiment, it provides automatic bobbing, a controllable force to urge the tool against the work, and sensibly constant force as the tool penetrates the work.

Using my apparatus, drilling, cutting, and other, procedures are according to the prior art and are not discussed since such procedures are well known to those skilled in the art. I

the moving ele- Particular examples of my invention, and further explanation of the principles thereof, are described below with reference to the drawings. In the drawings:

Description of the drawings FIGURE 1 is a front elevation of an embodiment of the invention adapted for attachment of a common electric drill thereto,

FIGURE 2 is a side view of showing the electric drill attached,

FIGURE 3 is a diagram showing a portion of the friction drive train as viewed from line 33 of FIGURE 2,

FIGURE 4 is a detail showing an alternative adjustable tension spring mounting means.

FIGURE 5 is a diagram to illustrate the principles of my invention,

FIGURE 6 has a helical spring added to the pull down cable of the FIGURE 5 structure.

DESCRIPTION OF PREFERRED EMBODIMENTS Description of FIGURES 1 and Z In FIGURE 1, the apparatus is indicated generally by the nueral 10. A frame assembly 11 is obviously slidable on left and right vertical guides 12, 13, top ends of which are secured to a transverse member 14. The guides are further secured to the base of the machine. A lever 15 is pivoted at 16 to a top corner of the frame, which lever extends beyond the frame to an outer end 17 remote from the pivot 16. A pull down cable 18 is attached to the lever at 19, adjacent the outer end 17 thereof. The other end of the cable 18 is secured to the periphery of a winding drum 2ft journalled on a fixed shaft 21 secured to a side of a counterweight 22. The shaft is threaded to receive a locking wing nut 23, tightening of which locks the drum preventing it from rotation upon the shaft 21. A resilient regulating means, the helical regulating spring 24, is inserted in the pull down cable 18 between the points of attachment thereof to the lever and drum. A cam roller 25 is attached to the lever 15 between the pivot point 16 and attachment point 19. A cam, indicated generally at 26, is keyed on a shaft 27 journalled in the frame assembly 11. The cam, later described in detail, has dwell portion 28, here shown in engagement with the cam roller aforesaid.

The transverse member 14 extends outwards of the guide 13, and is provided with a latch 29 cooperating with a pin29A of the frame assembly 11 so that, as a safety precaution, the assembly may be releasably secured to the transverse member 14 in an up position. A pull up cable 30 is. attached to the frame centrally between the guides as shown at 31. The pull up cable leads vertically upwards to a pulley 32 secured to the transverse member 14, thence around a pulley 33 at the outer end of the transverse member, and vertically downwards to a point of attachment to the counterweight 22, as shown at 34.

In FIGURE 2, a common inch electric drill 35 is secured in a usual manner to the frame assembly 11 midway between the vertical guides 12, 13, so that the drill axis is parallel to the guides. i.e. the said axis is vertical. I employ the electric drill to effect rotation of the cam, this is accomplished using a friction drive.

The electric drill has a chuck having a cylindrical portion 36. A friction collar 37 is secured to the cylindrical chuck portion aforesaid. The collar 37 drives a friction train now to be described, thereby rotating the cam 26.

The frame assembly 11 has a front plate 38 and a rear plate 39, the shaft 27 aforesaid is journalled in the plates at 40 and 41. A large pulley wheel 42 is keyed to said shaft, thus rotation of the pulley Wheel rotates the cam which, as before stated, is also keyed to the shaft 27. A second shaft 43 is similarly journalled in the front and rear plates 38, 39, to which shaft is keyed a small pulley 44, driving the large pulley aforesaid by means of the belt 45. A member 46 is also keyed to the shaft 43, which member has at least two splines 47 extending outwards away from the small pulley 44. A large friction disc 48 is slidable axially of the said shaft on the splines 47, so that rotation of the large friction disc shall rotate the shaft 43, and the small pulley 44.

Description 0 FIGURES 3 and 4 When the drill chuck portion 36 and friction collar 37 thereof are revolving, a spring closed friction train effects rotation of the large friction disc 48. FIGURE 3 is a simplified diagram showing the above friction train as viewed from line 33 of FIGURE 2. As best seen in FIGURE 3, a small face Wheel 49 is journalled on a short vertical shaft 50 of a horizontal arm 51 swingingly mounted at 51A to a convenient adjacent frame portion, not shown. A second small face wheel 52 is similarly mounted on a swinging arm 53 pivoted to the frame as shown at 54, constructed so that the pitch circles of the two small face wheels are coplanar and spaced to accommodate the large friction disc 48 between them. The pitch circle of the chuck collar 37 aforesaid lies in the same plane as the pitch circles of the wheels 49 and 52, and is in a position, as shown, adapted for operative engagement with the wheel 52. One end of a helical tension spring 55 is attached to the spring arm 51 remote from the point 51A, the other end of the spring is attached to any convenient frame member, as indicated at 56. Since the friction wheel 48 is slidable on the splines 47 (which are not shown in FIGURE 3) it is seen that, the chuck portion 36 and driving collar 37 thereof being attached to the frame, the tension spring 55 urges the members 37, 52, 48, 49 into engagement, whereby the large friction disc is rotated, hence to rotate the cam 26. This arrangement makes it necessary to mount the electric drill only so that its axis is vertical, and so that the chuck driving collar shall be in the proper vertical position to engage the small face axis 55. The spring and spline means above described permits considerable tolerance in the distance of the axis thereof from the frame plate 39, which permits power drills of different sizes and shapes to be mounted without undue difficulty.

FIGURE 4 shows an alternative means of attaching the spring 55 to a convenient adjacent frame part 53A. The spring 55 is attached to an end of a bolt 57 passing through a frame portion at 58 and held by an adjusting nut 59. Tightening or loosening the nut 59 will increase or decrease the tension of the spring 55, thus permitting adjustment of the pressure independently of the distance of the drill axis from the frame plate 39.

The drilling elements are according to the prior art. For example, a shank 60 of a tubular bit 61 is inserted in a chuck 62 of the electric drill aforesaid. Work 63 is fastened to a support 64 forming the base of the machine, to which base the vertical guides 12, 13 are secured as aforesaid and a grit cup 62 is provided.

Description of FIGURES 5 and 6 The principles of my invention are illustrated diagrammatically in FIGURES 5 and 6.

The discussion following refers to FIGURE 5, in the discussion friction is neglected and the cables are assumed to be inextensible. The weight of frame assembly 11 with the electric drill attached is W pounds, acting downwards upon the assembly as indicated by the vector W. The weight of the counterweight 20 is C pounds, also acting downwards as shown by the vector C. C is greater than W. With the pull up cable 30 slack, the force C is transmitted to the assembly 11 by the arm 15 bearing against the cam 26, thus to urge the assembly downwards. Hence, with the pull up cable slack, the total force urging the assembly 11 downwards, that is the force available to urge the bit 58 against the work piece (not here shown) is W+C pounds. The slackening of the pull up cable 30 as aforesaid would of course take place if the full load W+C were developed between the bit 58 and the work piece. When the bit 58 is not in contact with the work piece, the condition shown in FIGURE 5, a tension Tu develops in the pull up cable 30 and the system is stationary. In the said condition the downward forces on the assembly 11 are balanced by the upwards force thereon, the tension Tu developed in the pull up cable 30. That is, Tu: W+C. In this condition Tu=(C+W)/2 and, where Td is the tension in the pull down cable, Td: C W 2.

For example, if W: 16 and 0:18, then Tu=17 pounds and Td=l pound.

Still referring to FIGURE 5, it is seen that the rest, or equilibrium, position of the assembly 11 with reference to the fixed guides 12, 13, depends upon the efiective length of the pull down cable 18-the effective length of the pull up cable 30 being unchanged. Hence if the counter weight winding drum 26 be turned to lengthen the pull down cable 18, the counterweight 22 will move downwards causing the assembly 11 to move upwards-and vice versa. This provides means of lowering the bit to the Work, and raising it from the work. However, notwithstanding in practice the cables would have some extensibility, it is seen that (substantially) the full load C+W would be developed upon contact with the work, and that the bit would bottom, i.e. come to rest, after such small penetration as would result from extensibility in the cables. Thus vertical travel of the bit would not be automatic, and the bitwould be urged against the -work with an initial force approaching C+ W, to decrease rapidly to zero at bottoming. The above arrangement, namely alteration of the effective length of the pull down cable, would thus not attain desirable automatic regulation of the force urging the bit against the work.

I overcome these difficulties and attain automatic downward travel as well as automatic, sensibly constant controllable force, by inserting a helical regulating spring in the pull up cable, as shown in FIGURE 6 by the numeral 24. In the FIGURE 6 arrangement it is seen that the bit may be lowered to contact the work by rotating the counterweight drum 20 as above, and that the initial force urging the bit against the work is controllable by further turning of the drum after initial contact. It is also seen that the drill will, because of the spring, continue to move downwards as it penetrates the work. It is also seen that the initial force would decrease only in accordance with the decrease in Td as the length of the spring decreases with the down-wards motion of the bit. For example, if I use a spring having a force constant of 3 lb./in. then penetration of as much as a quarter of an inch will decrease the force by 12 ounces. The initial force applied depends upon the decrease in Td after contact, which force depends upon the amount of rotation of the drum. It is apparent that I may change the force, if necessary, at any stage of the drilling operation by suitable rotation of the drum to increase or decrease the spring tension.

If I use a spring such that extension of the length thereof under a load of C pounds is within the range permitted by the drum, I can develop the full force C+W between the work and the bit. With a such spring having a high force constant, pressure regulation would be coarse. With a smaller force constant the regulation would be finer. Thus, by choice of a spring in accordance with the requirements I am able to attain nice initial force regulation, sensible constant force during penetration, and automatic downward travel of the bit. It is to be understood that a regulating spring capable of bearing the full load of the counterweight C, thus to attain the maximum force C+W, is the high limit. Springs capable of bearing a smaller load may be used since it is not ordinarily required to develop the full rC+ W load. With a such spring, the fineness of regulation attainable is, as before, a function of the force constant-and of course a function of the drum diameter.

I have found that springs having a force constant of from about 3 to about 15 pounds per inch are satisfactory for lapidary work, and are suitable where penetration up to, say, two inches is required. I find that a set of five springs,

6 of strength such as to extend an inch under loads of about 3, 6, 9, l2, and 15 pounds respectively, will satisfy common requirements. Those skilled in the art will readily learn with experience which spring strength functions best for a particular piece of 'work, and may wish to exceed these limits in some circumstances.

The spring itself may be a simple helical spring wound of steel wire to suitable dimensions, or may be of other resilient material such as rubber. As well, equivalent action may be obtained by pneumatic means, for instance means including a piston movable within a closed cylinder. It is essential only that there be resilient action such that a cable shall change in effective length according to the load on it. Any means to accomplish this end will serve my purpose.

Bobbing is effected as follows. Referring to FIGURE 1, it is seen that the cam surface has a constant diameter dwell portion 28, a sensibly radial fall portion 28A and a rise portion 28B. The cam rotates in the direction of the arrow, thus the lever 15 remains at the full line position shown throughout the drive period-and assumes the position ISA once per cam revolution. At position 15A the effect is the same as that of lengthening the pull down cable 18 as described above with reference to FIGURES 5 and 6, namely to cause the assembly 11 to move upwards thus withdrawing the bit from the work, once per cam revolution. Thus, additionally my apparatus attains automatic bobbing action. The shape of the cam rise and fall portions is not critical, a cam shaped as shown gives satisfactory results.

It is apparent, see again FIGURE 6, that a couple tending to rotate the frame assembly 11 clockwise is developed, which couple is balanced by the reactions of the guides upon the assembly. This couple is in the plane of FIGURE 6, and arises from the counterweight.

The net downward force urging the drill bit against the work is balanced by an upwards axial reaction of the work against the bit. Since these two parallel forces are not aligned, a couple appears in a plane normal to the plane of the paper in FIGURE 6, which couple is balanced by an equal and opposite couple arising from guide reactions in this plane.

FURTHER CONSIDERATIONS AND ALTERNATIVES The counterweight 22 and associated structure may be duplicated by like structure on the left hand side of FIG- URE 6. In such configuration the aforesaid couple in the plane of the figure could be balanced out, rather than taken up by guide reactions. As well, the couple aforesaid normal to the plane of the figure may, by suitable balancing weights secured to the frame, be balanced or reduced. These matters are well understood in the art relating to drilling machines generally.

Mechanically, it is required that the guides 12, 13, be straight and parallel, and that the drill mounting be such that its axis is parallel to the guides. These matters too are well known in the art, therefore details of mechanical structure and tolerance are not given. However, in a such apparatus of high quality adapted for continual professional use, I prefer that adjustable ball or roller bearing means be'used so that the frame assembly 11 may be accurately aligned with respect to, and move with ease upon, the guides. For amateur lapidary use, simple sliding means are satisfactory. With alignment as above, the bit is movable only in a straight line, viz. the drill axis. Thus it is not possible to load the bit other than axially, except if a nonaxial reaction were to arise between the work and the bit.

The friction gear train described to rotate the cam 26 is simple, cheap, and effective.

Bobbing frequency, that is cam r.p.m., may vary within wide limits. Frequencies of from six or eight to about ten times that figure are acceptable. Bob frequency between the limits of six and eighty per minute is readily attainable from the simple friction train described using a common quarter inch electric drill.

However, any means to cause the required cam motion may be used, for instance a worm reduction train. As well, the cam may be dispensed with and, for example, a solenoid and external means to actuate the solenoid periodically may be used. The lever 15 is not essential, cam or solenoid plunger or rod means may be substituted for the lever, or in fact substantially any means to cause change in effective cable length may be used.

It is also apparent from the discussion of FIGURES 5 and 6 above, and from examination of these figures, that increase of the effective length of the pull up cable 3tl the pull down cable being of fixed length-will efiect as downward motion of the assembly 11.

Thus I may achieve the objects of my invention by altering the effective length of the pull up cable. I prefer however to use the embodiment of FIGURE 6 because, as has been shown, Td is much less than Tu. As well, whether the FIGURE 6 structure is used or whether the effective length of the pull up cable is to be altered, the regulating spring 26, or other resilient element, may be inserted in the pull up cable rather than in the pull down cable as shown. Different resilient characteristics would of course be required, but the regulating action attained in each case is the same in substance.

In the foregoing I have used cable and pulley imeans operatively connecting the counterweight with the assembly 11. Rigid linkage, or a combination of flexible and rigid links may be used to obtain action equivalent to that I have described.

The apparatus has been described in embodiments adapted to utilize a common quarter inch electric drill. Such embodiments are well adapted for amateur lapidary use. The particular apparatus may be used with any hand power drill, for instance a pneumatic powered drill.

Obviously, the counterweight and associated means as described in detail are applicable when the frame assembly 11 includes, in lieu of a detachable hand power drill, a shaft adapted for attachment of a drill bit or other tool thereto, and for instance belt and cone pulley means to rotate the shaft from a suitable motor.

The substance of my invention as disclosed in the embodiments and examples above is basically a means for the repetitive application of a controlled force. This I apply by means of a vertically movable element having a counterweight operatively connected thereto by pull up moving means tending to move it upwards-the weight of the counterweight being greater than that of the movable element, by pull down means operatively connected to the moving element to tend to pull it downwards, by means periodically to alter the effective length of a said moving means, and by resilient regulating means forming an operative part of a said moving means.

It is apparent that the structure of my invention may be used in other circumstances where it is required to apply a controlled force for a determinate length of time, to release the force and again to apply it after a determinate time interval, repeating a cycle. In the drill embodiment, the force is applied to urge the bit against the work for an interval of time, after which the force is released and the bit moves upwards away from the work, and is reapplied to repeat the cycle. In the drilling cycle, the time in contact with the work is much greater than the bobbing, or release, time. Any required proportion is obviously attainable by varying the cam dwell. The time of one complete cycle may be varied at will and, in a single lobe cam, is the cam r.p.m.

An example of another use of my invention is in spot gluing operations of a certain kind, where it is required that a load, say 20 pounds, be applied to urge two surfaces together at a point to which a spot of contact adhesive has been applied to each surface, to maintain that load for, say, three seconds, then to release the load for, say, one second to permit the work, or the apparatus, to be advanced to a second spot at which the cycle is reill peated. My mechanism is well suited to such an operation: a cam having 270 of dwell revolving at 15 rpm. would give a 3 second off cycle, to apply the required load.

Those skilled in the relevant arts will find obvious application of the essence of my invention in a variety of other apparatus requiring cyclic application and release of a determinate load.

Iclaim:

ll. An apparatus for repetitive application of a controlled force, which apparatus is characterized by a combination having:

(a) a vertically moving element having a weight W,

the said element being constrained to lineal motion,

(b) a counterweight of weight C where C is greater than W,

(o) pull up moving means operatively connecting the counterweight to the vertically moving element to tend to move the latter upwards,

(d) pull down moving means operatively connecting the counterweight to the vertically moving element to tend to move the latter downwards,

(e) means periodically to alter the effective length of one said moving means,

(f) and resilient regulating means forming an operative part of a said moving means.

2. Apparatus as described in claim 1 in which; the pull up means is a cable leading upwards from the counterweight and around a pulley, to a point of attachment on the vertically moving element; and in which the pull down means is a cable secured to the counterweight and operatively connected to the element (e) aforesaid.

3. Apparatus as described in claim 2 in which the means of securing the pull down cable to the counterweight is a rotatable drum constructed and arranged to 'wind or unwind a portion of the pull down cable around the drum, and means to lock the drum to prevent rotation thereof.

4. Apparatus as claimed in claim 3, in which the resilient regulating means is an operative part of the pull down cable moving means.

5. Apparatus as described in claim 1 in which the element (e) includes a rotatable cam of the vertically moving element, and means to rotate the cam.

6. Apparatus as claimed in claim 4, in which the element (e) includes a rotatable cam of the vertically moving element, and means to rotate the cam.

7. Apparatus as described in claim 1, in which the element (e) includes a rotatable cam of the vertically moving element, and means to rotate the cam, a lever pivoted to the vertically moving element, the lever being adapted to cooperate with the cam so that rotation of the cam shall cause the lever to oscillate about the pivot thereof, and in which an end of the pull down cable is attached to an end of the lever remote from the cam, so that rotation of the cam causes periodic alteration of the effective length of the pull up means.

8. Apparatus as described in claim 6 in which the element (e) further includes; a lever pivoted to the vertically moving element, the lever being adapted to cooperate with the cam so that rotation of the cam shall cause the lever to oscillate about the pivot thereof, and in which an end of the pull down cable is attached to an end of the lever remote from the cam, so that rotation of the cam causes periodic alteration of the effective length of the pull up means.

9. Apparatus as described in claim 8 further characterized in that the vertically moving element includes a rotating shaft adapted for attachment of a tool thereto, together with a speed reduction train constructed and arranged so that rotation of the shaft aforesaid shall rotate the cam at a lower speed than that of the shaft.

10. Apparatus as described in claim 9, wherein the reduction train is such as to rotate the cam at a speed between about six and about eighty revolutions per minute.

11. Apparatus as described in claim 9, wherein the resilient regulating means is capable of lineal extension and has a force constant of from about three to about fifteen pounds per inch.

12. Apparatus as described in claim 10, wherein the resilient regulating means is capable of lineal extension and has a force constant of from about three to about fifteen pounds per inch.

13. Apparatus as described in claim 7, wherein the vertically moving element is adapted for attachment of a common hand power drill thereto, and in which the means to rotate the cam is a speed reduction train activated by rotation of a shaft of the power drill.

14. Apparatus as described in claim 8, wherein the vertically moving element is adapted for attachment of a common hand power drill thereto, and in which the means to rotate the cam is a speed reduction train activated by rotation of a shaft of the power drill.

15. Apparatus as described in claim 9, wherein the vertically moving element is adapted for attachment of a common hand power drill thereto, and in which the means to rotate the cam is a rotating shaft of the power drill.

16. Apparatus as described in claim 12, wherein the vertically moving element is adapted for attachment of a common hand power drill thereto, and in which the means to rotate the cam is a rotating shaft of the power drill.

17. Apparatus as described in claim 7 wherein the speed reduction train mcludes; a pair of swingingly mounted face wheels, spring means to urge the face wheels in engagement with faces of a friction disc, and to urge one face wheel in engagement with a driving friction collar of the power drill, and wherein the friction disc is slidably secured to a shaft, constructed and arranged so that drive is secured throughout a range of slidable motion of the friction disc as aforesaid.

18. Apparatus as claimed in claim 17, wherein the spring urging means is adjustable, and is adapted to vary the force with which the face wheels are urged in engagement with the friction disc and the collar.

19. Apparatus as claimed in claim 16, wherein the speed reduction train includes; a pair of swingingly mounted face wheels, spring means to urge the face wheels in engagement with faces of a friction disc, and to urge one face wheel in engagement with a driving friction collar of the power drill, and wherein the friction disc is slidably secured to a shaft, constructed and arranged so that drive is secured throughout a range of slidable motion of the friction disc as aforesaid.

20. Apparatus as claimed in claim 19, wherein the spring urging means is adjustable, and is adapted to vary the force with which the face wheels are urged in engagement with the friction disc and the collar.

References Cited UNITED STATES PATENTS 24,449 6/ 1859 Emery -2 42,167 4/1864 Cody 173-147 1,005,271 10/1911 Mills 100-268 X 2,810,308 10/1957 Bodmer 77-36 X HAROLD D. WHITEHEAD, Primary Examiner. 

1. AN APPARATUS FOR REPETITIVE APPLICATION OF CONTROLLED FORCE, WHICH APPARATUS IS CHARACTERIZED BY A COMBINATION HAVING: (A) A VERTICALLY MOVING ELEMENT HAVING A WEIGHT W, THE SAID ELEMENT BEING CONSTRAINED TO LINEAL MOTION, (B) A COUNTERWEIGHT OF WEIGHT C WHERE C IS GREATER THAN W, (C) PULL UP MOVING MEANS OPERATIVELY CONNECTING THE COUNTERWEIGHT TO THE VERTICALLY MOVING ELEMENT TO TEND TO MOVE THE LATTER UPWARDS, (D) PULL DOWN MOVING MEANS OPERATIVELY CONNECTING THE COUNTERWEIGHT TO THE VERTICALLY MOVING ELEMENT TO TEND TO MOVE THE LATTER DOWNWARDS, (E) MEANS PERIODICALLY TO ALTER THE EFFECT LENGTH OF ONE SAID MOVING MEANS, (F) AND RESILIENT REGULATING MEANS FORMING AN OPERATIVE PART OF A SAID MOVING MEANS. 